Layers and Workspaces¶

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A Layer represents a particular set of spatial data. It contains methods that provide information about a data set such as the count of entries and the spatial bounds of the data.

>>> from geoscript.layer import Shapefile
>>> shp = Shapefile('states.shp')

>>> shp.count()
49
>>> shp.bounds()
(-124.731422, 24.955967, -66.969849, 49.371735, EPSG:4326)

Note

In the above code sample the layer.Shapefile class is a layer subclass specific to the Shapefile format.

>> var Directory = require("geoscript/workspace").Directory;
>> var shp = new Directory("data/shp").get("states");
>> shp
<Layer name: states, count: 49>
>> shp.count
49
>> shp.bounds
<Bounds [-124.73142200000001, 24.955967, -66.969849, 49.371735] EPSG...>

scala> import org.geoscript.layer._
scala> val shp = Shapefile("states.shp")
shp: org.geoscript.layer.Layer = <Layer name: states, count: 49>

scala> shp.count
res0: Int = 49

scala> shp.bounds
res1: (Double, Double, Double, Double, String) = (-124.73142200000001,24.955967,-66.969849,49.371735,EPSG:4326)

groovy:000> import geoscript.layer.Shapefile
===> [import geoscript.layer.Shapefile]

groovy:000> shp = new Shapefile('data/shp/states.shp')
===> geoscript.layer.Shapefile@4597871d

groovy:000> shp.count()
===> 49

groovy:000> shp.bounds()
===> (-124.73142200000001,24.955967,-66.969849,49.371735,EPSG:4326)

Each entry in a Layer is known as a feature and represented by the Feature class (in the feature module). A feature is a set of attributes and an associated geometry. You can iterate through all features on a layer to access feature information.

>>> for f in shp.features():
>>>    print f
states.1 {the_geom: MULTIPOLYGON (((-88.071564 37.51099000000001, ... ,-88.071564 37.51099000000001))), STATE_NAME: Illinois, STATE_FIPS: 17, SUB_REGION: E N Cen, STATE_ABBR: IL, LAND_KM: 143986.61, WATER_KM: 1993.335, PERSONS: 11430602.0, FAMILIES: 2924880.0, HOUSHOLD: 4202240.0, MALE: 5552233.0, FEMALE: 5878369.0, WORKERS: 4199206.0, DRVALONE: 3741715.0, CARPOOL: 652603.0, PUBTRANS: 538071.0, EMPLOYED: 5417967.0, UNEMPLOY: 385040.0, SERVICE: 1360159.0, MANUAL: 828906.0, P_MALE: 0.486, P_FEMALE: 0.514, SAMP_POP: 1747776.0}
...

>> shp.features.forEach(function(feature) {
  >     print(feature);
  > });
<Feature the_geom: <MultiPolygon>, STATE_NAME: "Illinois", STATE_FIPS...>
<Feature the_geom: <MultiPolygon>, STATE_NAME: "District of Columbia"...>
<Feature the_geom: <MultiPolygon>, STATE_NAME: "Delaware", STATE_FIPS...>
...

scala> for (feature <- shp.features) { println(f) }
<Feature EMPLOYED: 5417967.0, ... the_geom: <MultiPolygon>, PUBTRANS: ... >
<Feature EMPLOYED: 303994.0,  ... the_geom: <MultiPolygon>, PUBTRANS: ... >
<Feature EMPLOYED: 335147.0,  ... the_geom: <MultiPolygon>, PUBTRANS: ... >

groovy:000> shp.features.each{f -> println(f)}
states.1 the_geom: MULTIPOLYGON (((-88.071564 37.51099000000001, ...
states.2 the_geom: MULTIPOLYGON (((-77.008232 38.966556999999995, ...

A layer schema is a set of field descriptions that describe the structure of the data in the layer’s features.

>>> shp.schema
states [the_geom: MultiPolygon, STATE_NAME: str, STATE_FIPS: str, SUB_REGION: str, STATE_ABBR: str, LAND_KM: float, WATER_KM: float, PERSONS: float, FAMILIES: float, HOUSHOLD: float, MALE: float, FEMALE: float, WORKERS: float, DRVALONE: float, CARPOOL: float, PUBTRANS: float, EMPLOYED: float, UNEMPLOY: float, SERVICE: float, MANUAL: float, P_MALE: float, P_FEMALE: float, SAMP_POP: float]

>> shp.schema
<Schema name: "states", fields: [{"name": "the_geom", "type": "Multi...>

scala> shp.schema
res0: org.geoscript.layer.Schema = <Schema name: states, fields: [the_geom: MultiPolygon, STATE_NAME: String, STATE_FIPS: String, SUB_REGION: String, STATE_ABBR: String, LAND_KM: Double, WATER_KM: Double, PERSONS: Double, FAMILIES: Double, HOUSHOLD: Double, MALE: Double, FEMALE: Double, WORKERS: Double, DRVALONE: Double, CARPOOL: Double, PUBTRANS: Double, EMPLOYED: Double, UNEMPLOY: D...

groovy:000> shp.schema
===> states the_geom: MultiPolygon(EPSG:4326), STATE_NAME: String, STATE_FIPS: String, SUB_REGION: String, STATE_ABBR: String, LAND_KM: java.lang.Double, WATER_KM: java.lang.Double, PERSONS: java.lang.Double, FAMILIES: java.lang.Double, HOUSHOLD: java.lang.Double, MALE: java.lang.Double, FEMALE: java.lang.Double, WORKERS: java.lang.Double, DRVALONE: java.lang.Double, CARPOOL: java.lang.Double, PUBTRANS: java.lang.Double, EMPLOYED: java.lang.Double, UNEMPLOY: java.lang.Double, SERVICE: java.lang.Double, MANUAL: java.lang.Double, P_MALE: java.lang.Double, P_FEMALE: java.lang.Double, SAMP_POP: java.lang.Double

A schema is comprised of fields that describe each attribute of a feature. A field describes the name and the type of a feature attribute. A list of field names can be accessed for a schema, and individual field descriptors can be accessed given a field name.

>>> f = shp.schema.get('STATE_NAME')
>>> f.name
'STATE_NAME'
>>> f.typ
<type 'str'>

>> shp.schema.fieldNames
the_geom,STATE_NAME,STATE_FIPS,SUB_REGION,STATE_ABBR,LAND_KM,WATER_KM,PERSONS,FAMILIES,HOUSHOLD,MALE,FEMALE,WORKERS,DRVALONE,CARPOOL,PUBTRANS,EMPLOYED,UNEMPLOY,SERVICE,MANUAL,P_MALE,P_FEMALE,SAMP_POP

>> var field = shp.schema.get("STATE_NAME");
>> field.name
STATE_NAME
>> field.type
String

scala> shp.schema.fieldNames
res1: Seq[String] = ArrayBufferRO(the_geom, STATE_NAME, STATE_FIPS, SUB_REGION, STATE_ABBR, LAND_KM, WATER_KM, PERSONS, FAMILIES, HOUSHOLD, MALE, FEMALE, WORKERS, DRVALONE, CARPOOL, PUBTRANS, EMPLOYED, UNEMPLOY, SERVICE, MANUAL, P_MALE, P_FEMALE, SAMP_POP)

scala> shp.schema.get("STATE_NAME")
res2: org.geoscript.layer.Field = STATE_NAME: String

scala> res2.name
res3: String = STATE_NAME

scala> res2.binding
res4: java.lang.Class[_] = class java.lang.String

groovy:000> f = shp.schema.field('STATE_NAME')
===> STATE_NAME: String

groovy:000> f.name
===> STATE_NAME

groovy:000> f.typ
===> String

Every layer object is part of a Workspace. A workspace is a collection of layers. You can retrieve a list of layer names for a workspace as follows:

>>> ws = shp.workspace
>>> ws
Directory[/Users/bob]
>>> ws.layers()
['counties', 'states']

Note

The layer.shapefile.Shapefile layer is implicitly part of a workspace.Directory workspace. The layers of a directory workspace correspond to the spatial files in the directory.

>> var dir = shp.workspace;
>> dir
<Directory ["states"]>
>> dir.names
states

scala> val dir = shp.workspace
dir: org.geoscript.workspace.Workspace = <Directory: [file:/data/]>

scala> dir.names
res1: Seq[String] = Array(states)

groovy:000> dir = shp.workspace
===> Directory[/Users/jericks/Downloads/data/shp/]

groovy:000> dir.layers
===> [states]

Create a new layer and add it to an existing workspace as follows:

>>> from geoscript import geom
>>> l = ws.create('cities', [('geom', geom.Point), ('name', str)])
>>> ws.layers()
['cities', 'counties', 'states']
>>> l.count()
0
>>> l.add([geom.Point(37.78, -122.42), 'San Francisco'])
>>> l.add([geom.Point(40.47, -73.58), 'New York'])
>>> l.count()
2

>> var Layer = require("geoscript/layer").Layer;
>> var cities = new Layer({
  >     name: "cities",
  >     fields: [{
  >         name: "name", type: "String"
  >     }, {
  >         name: "geom", type: "Point"
  >     }]
  > });
>> dir.add(cities);
>> var GEOM = require("geoscript/geom");
>> cities.add({name: "San Francisco", geom: new GEOM.Point([-122.42, 37.78])});
>> cities.add({name: "New York", geom: new GEOM.Point([-73.58, 40.47])});
>> cities.count
2

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